1. Field of the Invention
This invention relates to an image forming, transferring or recording system which utilizes a pressure-sensitive photosensitive medium having a surface coated with a photosensitive material. More particularly, the present invention is concerned with such an image forming system which includes an exposing device for irradiating the photosensitive surface of the photosensitive medium with a radiation and thereby forming a latent image on the photosensitive surface according to an amount of exposure of the surface to the radiation, and which further includes a developing device in the form of a pressing device having a first and a second member which cooperate with each other to press or squeeze the exposed medium therebetween, for thereby developing the latent image into a visible image.
2. Discussion of the Prior Art
A known image forming system of the type indicated above uses, for example, a photosensitive material and a developer material which are capable of chemically reacting with each other and producing a color image. Described more specifically, the latent image is developed into a visible image by the chemical reaction between the photosensitive and developer materials. This developing process is carried out by the developing device, which is adapted to apply a pressure to the photosensitive medium and thereby causing the photosensitive and developer materials to be mixed with each other, for chemical reaction therebetween. The developer material may be provided as a developer layer on the photosensitive medium which has a photosensitive layer made of the photosensitive material. Alternatively, the developer material is provided on a separate developer medium. In this latter case, the developer medium is superposed on the photosensitive medium such that the developer layer and the photosensitive layer of the two media are held in contact with each other. The superposed two media are then pressed by the developing device, for chemical reaction between the developer and photosensitive materials for producing a visible image. In the former case wherein the photosensitive medium also has the developer layer, the visible image is formed on the photosensitive medium. In the latter case, the visible image is created on the developer medium, which serves as a recording medium.
In the former case where the photosensitive medium has a developer layer, one of the first and second members of the developing or pressing device directly contacts the photosensitive surface of the medium. In the latter case where a separate developer medium is used, one of the first and second members of the pressing device indirectly contacts the photosensitive medium via the developer medium superposed thereon. Since the photosensitive medium usually has a larger surface area than the developer medium, the photosensitive medium has a portion which is left uncovered. Therefore, the first or second member of the pressing device directly contacts the uncovered portion of the photosensitive medium. Thus, in either case, the photosensitive material inevitably adheres to the first or second member of the pressing device during the developing process. In the former case, the photosensitive material soils the photosensitive surface of the photosensitive medium on which the visible images are formed. In the latter case, the photosensitive material adheres to the back surface of the developer medium opposite to its surface (developer layer) contacting the photosensitive surface of the photosensitive medium. Hence, it is necessary to wipe off the photosensitive material from the first or second member of the pressing device.
However, the cleaning procedure to wipe off the photosensitive material from the presser member is cumbersome and time-consuming, particularly where the presser member has a curved pressure surface, or a complicated construction that prevents easy cleaning of the pressure surface. If the cleaning of the presser member is automatically cleaned, the cleaning operation requires a relatively complicated cleaning device.
The cleaning job is particularly troublesome where the developing or pressing device uses a presser member having a relatively narrow contact area or a contact point, which is moved at a high speed in contact with the surface of the photosensitive medium, so that the path taken by the contact area or point covers the entire surface area of the photosensitive medium. In this case, the narrow contact area or contact point is heavily contaminated with the photosensitive material transferred from the photosensitive medium. Consequently, the photosensitive surface of the photosensitive medium, or the back surface of the developer medium is locally heavily soiled with the photosensitive material adhering to the presser member.